Another important point illustrated by Fig. REF  concerns
the photometric activity of SU Lyn. The star is too bright to be recorded
unsaturated by surveys which monitor the heaven on a nightly basis in search
for transients (eg. ASAS-SN, MASTER, ZTF, etc.), therefore we monitored it
ourselves with small instruments, and fully transformed the observations to
the [1]} standard UBVRI system. As illustrated by
the \(B\) ,\(V\)  lightcurve on the right panel of Fig. REF 
(synchronized to the same temporal ordinates as the spectra to the left),
SU Lyn varies by up to 0.7 mag amplitude in a random fashion, with no
persistent periodicity. There is no associated change in colour and no
correspondence with the behavior of the accretion disk as traced by
H\(\alpha \)  intensity and profile. Thus, the variability is not caused by
brightening and fading of the accretion disk (hotter than the M6III), but
must originate with the cool giant. All cool giants exhibit variability to
some extent [2]}, [3]}, given the
unstable nature of their convective outer layers
[4]}, and their tenuous atmosphere that extends
across the temperatures for molecule formation and through those for dust
condensation. The absence of radial velocity variability on the left panel
of Fig. REF  precludes an origin of the variability seen in
SU Lyn with the coherent, large scale, persistent radial pulsations of the
type observed in Mira long-period variables. The latter show a
sinusoid-like radial velocity curve of \(\sim \) 10-15 km s\(^{-1}\)  in amplitude,
in phase with the equally sinusoid-like lightcurve that can span up to 10
magnitude in amplitude, and characterized by bluer colour at maximum and
redder at minimum (see fig. 27 in [2]}).
